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Cooling of Overhead Water Tank in Summer

05/09/2011 2:32 PM

It is hot summer outside temp. is about 45c . the water tank which is located on roof and supply water to all my flat is dam hot , you need to keep the water taps open for 15 min . I want to design a mechanism to keep the water inside the tank cold at least 30c .

i thought of directing the water flow from the ground to a heat exchanger and then splatch it to the tank . will this works ? if not what is the possible and easy way to cool the water in the Tank ? i am looking for a costless design ? please help ? thankx.

Re: cooling of Overhead water tank in summer

Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.

Re: cooling of Overhead water tank in summer

05/09/2011 2:55 PM

Why you have a water tank on the roof? What supplies the water to the tank, the rain, a pipe from the city water system? To lower the temperature of the water in the tank (to about 45 degrees C) you can build a structure over the tank, so the sun doesn't fall directly, still, the water in the tank will have the ambient temperature. You might try a fabric wrapped around the tank. When wet, the energy to evaporate the water in the fabric will lower, a bit, the temperature in the tank. How much? No idea! If the water comes from the city water system (from the ground) make a branch directly to your needing place and you might have an even lower (14-20 degrees) temperature water. If none of the solutions works, you need a cooler type on the pipe coming from the tank.

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I wrote before reading the other comments. Sorry for redundancy

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Re: cooling of Overhead water tank in summer

05/09/2011 3:11 PM

the tank is getting fill from city water system with the help of a pump . water entering the tank is too hot and u need to keep it flowing for period of time in order to get it cool down . what u think if i place a heat exchanger at the inlet of the tank ?

Re: cooling of Overhead water tank in summer

05/09/2011 3:26 PM

If running the water for 15 minutes cools it down. Then the problem may not be the water is the tanks but the feed lines. Which are most likely laid exposed to the sun on the roof. You might try covering them. That's unless in the 15 minutes you are drawing down the water so much that the source that replenish it is cooling it down.

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Re: Cooling of Overhead Water Tank in Summer

05/09/2011 10:47 PM

Rather than try to cool the whole tank, you might like to make a small "Coolgarie" safe that cools the water as it is delivered into the house.

Coolgardie works on the evaporation principal. An outer container (say a perforated 200l drum) has 20m of copper water pipe coiled inside it and the interspace filled with charcoal blocks or similar porous material. The water supply flows through that pipe.

Air flow through the perforations enables evaporative cooling to happen. A slow but constant "drip" onto the porous material maintains the moisture levels for evaporation to continue.

Provides two benefits. You immediately have your cool water and as hotter water is drawn in, there is the thermal mass of the pipe and wet charcoal to cool that flow.

Large versions of these were used in outback as refrigerators on properties.

Re: Cooling of Overhead Water Tank in Summer

05/10/2011 10:43 AM

Yep! Remember them well.

Before people used refrigerators or they couldn't afford one, the coolgardie safe was used extensively in the hot Australian summers to keep dairy products and meat..........and boy the used to work well.

This reminded me of something similar............the hessian bag containing water that you used to hang on the font of the car.........not in front of the radiator..........and in summer that water used to be icy cold. Here is a photograph of one:

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Re: Cooling of Overhead Water Tank in Summer

05/10/2011 11:18 PM

Yes the waterbags were great.

I've been fortunate to be exposed to a variety of technology when travelling as a child. Been to places where "electricity" was introduced in 1978. (Ironically the same place had ISD and STD phones installed in 1970.)

Drip safes, ice chests, and so on in central Aus, it was the norm.

Waterbags in the shearing sheds was the only reliable way to have cool water when the nearest (electrical) fridge was 20 mile away, water mellons in hessian bags strung over fences (Even taught that to some Indians when I visited New Delhi.)

Re: Cooling of Overhead Water Tank in Summer

05/09/2011 11:45 PM

It is not the tank water that is getting heated up. It is the line coming from the tank to your tap, that is getting heated up. When water is not flowing, the water in this line will heat up and you will not get cool water from the tank, till you drain the complete water in this feed line to your tap, and the line itself attains the lower temperature.

So, don't do anything to tank. Just insulate the lines coming from tank to your tap, the problem will be solved.

With Sun, tank water will not heat much beyond about 35 deg C. Because of huge volume of the water in the tank, the water will not heat up in the tank. Even it will not cool much during night time, because of volume of water.

Re: Cooling of Overhead Water Tank in Summer

05/10/2011 12:57 AM

Simple way is use few buckets ,fill the water and allow it to cool in the shaded bath room. Other way is in summer water heater which is installed inside the bath room is rarely used . Use this water . Both these methods does not need any extra energy consumption and does not invlove any cost except the capital cost to buy a bucket.

Re: Cooling of Overhead Water Tank in Summer

05/10/2011 1:31 AM

mrswamy,

You said it! Use the water through the Storage water heater in the bathroom that is already cold (indoor, with heater electric power off). This is exactly what we are used to do in Muscat where the summer outdoor temperatures exceed 55degC.

Re: Cooling of Overhead Water Tank in Summer

Re: Cooling of Overhead Water Tank in Summer

05/10/2011 7:47 AM

Simple and economical way would be cover the tank top with jute bags or hessain cloth. and sprinkle water ocasionaly to keep the fabric wet. Due to evaporation of water, tank water will remain cool. Sprinkling system can be similar to garden sprinklers.

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Re: Cooling of Overhead Water Tank in Summer

What is your water tank made of? Is the city water line coming in accessible and exposed to sunlight? What is the water temperature at night after a few hours with no sunlight?

I suspect you are fighting radiant heat gain from the sun. You need a radiant barrier coating on the line and the tank.

We have dropped the surface temperature of a painted metal roof by 76-degrees.

We have dropped the air temperature coming into buildings by as much as 25-degrees just be coating the rooftop AC unit and a little metal ductwork. Many other examples on our website. Our URL is on my page.

I have coated small galvanized water pump storage tanks at homes. it dropped the water temperature by 30-degrees (on a hot summer day) . Prior to coating, they also had to let it run for around 15-minutes before it got cool. You could not touch the tank prior in the afternoon. Now it is cool all the time.